The present invention relates to a system for inspecting a forward end portion in a tunneling machine, and more particularly, to a system for inspecting a forward end in a tunneling machine such as a tunnel boring machine or a shield tunneling machine in which the wear of cutter bit or the properties of the ground or the like can be observed without discontinuing the tunneling work or removing the excavated soil.
Conventionally, a tunnel boring machine has been known as a tunneling machine which is employed to construct a tunnel in relatively solid ground.
In FIG. 1, this type of tunnel boring machine is shown. The tunnel boring machine includes a cylindrical main body 1 having both side ends open and a cutter plate 2 provided on an open forward end of the main body 1 having a hemispherical shape. On the cutter plate 2 are provided a plurality of roller-cutters 3 which are rotatably supported thereon and openings 4 for introducing the excavating soil between the roller-cutters 3. A disk-shaped partition wall 6 is provided inside the cutter plate 2 in a state where a sealing material 5 is interposed between the partition wall 6 and the inner periphery of the cutter plate 2, thereby defining a chamber 7 for accommodating the excavated soil at the rear of the cutter plate 2.
A motor 8 is provided adjacent to the outer periphery of the cutter plate 2 so that the cutter plate 2 is connected to the motor 8 through gears.
At the lower portion of the chamber 7, there is provided a nozzle 9 to which high-pressure water is supplied from a device provided at the rear of the main body 1. A discharge pipe 10 pierces through the partition wall 6 and is disposed in confrontation with the nozzle 9.
In the tunnel boring machine thus constructed, the cutter plate 2 is rotated by the motor 8 while thrusting the main body 1 forward by a propelling jack (not shown), thereby excavating the ground with the roller-cutters 3.
The excavated soil is introduced into the chamber 7 from the openings 4 and mixed with the water ejected from the nozzle 9 to form a slurry, and the soil in the form of a slurry is discharge to the outside through the discharge pipe 10.
By repeating the above operations, a tunnel is constructed by the tunnel boring machine. However, this type of tunneling machine is employed when excavating relatively solid ground, so that the roller-cutters are worn away in a short time. Therefore, in order to maintain the efficiency of excavation, the degree of wear on the roller-cutters must be known.
Although the properties of the ground to be excavated is investigated in advance, it is not grasped in detail, and therefore the state of ground and the excavated soil must be directly observed by one's eyes.
Thus, conventionally, a worker enters into the chamber 7 to inspect the state of wear in the roller-cutter 3 and the properties of the ground. However, such a method of inspecting has the following disadvantages.
That is, in the above inspection, since a worker enters into the chamber 7, the excavating operation must be discontinued, thus decreasing the efficiency of the excavation.
Further, in this type of tunnel boring machine, since the chamber 7 is not pressurized, as opposed to a shield tunneling machine, it is easier for a worker to enter into the chamber 7 as compared with the shield tunneling machine. However, since the excavated soil is accommodated in the chamber 7, the worker cannot enter into the chamber 7 unless the soil is removed therefrom. This removal of soil is troublesome work, due to the limited space inside the chamber.
On the other hand, in the shield tunneling machine, such as an earth pressure balance type or a slurry type of shield tunneling machine, excavation of a tunnel cannot be performed sometimes during shield tunneling, for some reason or other. This failure of excavation is caused by various reasons, including adhesion of soil to the chamber, obstructions in front of the cutter, wear or breakdown of the cutter bit, or the occurrence of cavities due to ground settlement.
In case of the occurrence of the above malfunctions, since the chamber in front of the partition wall is filled with muddy water or mud, and thus pressurized, the state inside the chamber cannot be easily observed.
Further, the cutter face not only cannot be observed by one's eyes, but wear or breakdown of the cutter bit cannot be directly inspected.
As a means for detecting the wear or breakdown of the cutter bit, there is a known wear detecting device using ultrasonic waves, for example, disclosed in Japanese Laid-Open Publication No. 60-144607. However, in this wear detecting device, wear of a detecting bit juxtaposed with cutter bits is detected, thereby estimating the wear degree of the other cutter bits. That is, the wear of a cutter bit is estimated from a detecting bit and as a result, the wear of the cutter bit cannot be accurately detected.